ZX1/2 laser readout system

Features

Implemented features (random order):

• analog readout through ADS
• digital readout (serial port)
• led/LCD
• USB com to PC (115200 8N1)

To be implemented features:

• Threshold settings in ADS?
• threshold setting in ZX2
• threshold processing for ZX1
• ZX1/2 identification
• Tune1/2/zero sequencing

Schematic

I/O list

Robot controller connector (ToRobotCtrl):

Pin	µC	meaning
1	gnd	Signal reference
2	DAC_out(P2.2)	Dac output from µC to robot controler, scaled down from 5 to 3.3V levels
3	Dig out (P2.6)	Digital output from µC to robot controler, scaled down from 5V to 3.3V levels
4	Dig in (P2.5)	Digital input from robot controller to µC, somehow protected
5	Analog out	ZX output scaled up to reach 3.3V levels (from 4-20mA)
6	Digital out	Comparison of previous signal against threshold set with R1, 3.3V levels
7	5V in (optional)	Optional 5V input from robot controller

TO CORRECT: R1 should be called P1, ToRobotCtrl should have a Jx name

USB connector:

• Standard µUSB-B connector, can be used to power the µC and all the 5V islands on the board. Thanks to power supplies monitoring, the board can report main power supplies are off.

Power supplies:

• Main 15-24V supply, Phoenix connector: will power the ZX sensors and the board itself (5V+12V regulators), resettable fuse protected (500mA)
  

  pin	meaning
  1	gnd
  2	15 to 24V in, 500mA max

Jack power connector: alternative to the main 12-24V connector, mostly useful for development and debugging. Parallel to other connector and protected using the same fuse. Not expected to provide 24V to J6 connector. * Auxiliary 12V connector: will bypass the 12V regulator for direct 12V powering from robot controller, resettable fuse protected (500mA)

pin	meaning
1	gnd
2	Not connected
2	12V in, 500mA max
pin	meaning
shield	gnd
tip (inside +)	15 to 24V in, 500mA max

• 5V is derived from the +12V power rail
• USB can also supply the +5V rail as backup supply. In normal conditions, the Schottky diode will prevent this.
• 12V regulator can provide 350mA, it requires a heatsink
• 5V regulator is expected to provide 75mA max.

ZX1/2 connector: is DB15 connector used to connect ZX sensors to board:

pin	ZX1	ZX2(wire color)	µC	Meaning
1	gnd(blue)	gnd(blue)		main gnd for sensor
2	judgement1(white)	low threshold(gray)	P0.6	first comparator output
3	tune2(pink)	reset/bank1(red)	P4.1
4		error output(yellow)	P0.3	only for ZX2
5	laser off(red)	laser off (pink)	P0.2
6	analog out+(black)	analog out+(black)	to ADS111x+/P3.5	this 4-20mA signal is going through 100Ω resistor then is differentially digitized by the ADS111x, also signal is scaled to 3.6V and wired to µC
7	zero(purple)	zero(orange)	P5.0
8	judgement2(green)	high threshold(white)	P0.7
9	tune1(orange)	timing/bank0(purple)	P4.0
10		pass(green)	P3.6	only for ZX2
11	analog out -(black shield)	analog out -(black shield)	to ADS111X -	GND for analog out, substracted by ADS111x and differential amplifier
12-14				NC
15	+12V(brown)	+12V(brown)		sensor main supply

ZX must be configured for 4-20mA output

DB9 serial connector for ZX2: used for digital communication to ZX2 sensor. It only features RX and TX with RS232 levels. Serial configuration is 38400bauds, 8N1 protocol.

pin	meaning ZX	meaning µC
2	TX	RX (P3.0)
3	RX	TX (P3.1)
5	gnd	gnd

µC I/O list

pin	port	meaning	oddities
28	P0.0	SWDIO	programmer port
29	P0.1	SWDCK	programmer port
30	P0.2	Laser off to ZX
31	P0.3	Error reading from ZX
32	P0.4	I²C SCL	I²C for ADS111x
33	P0.5	I²C SDA	I²C for ADS111x
34	P0.6	judgement 1/low from ZX
35	P0.7	judgement 2/high from ZX
48,1-6	P1[0-6]	Parallel LCD display
7	P1.7	LCD backlight PWM	is on PWMn output
10	P2.0	RX from computer	wired to MCP2221 TX
11	P2.1	TX to computer	wired to MCP2221 RX
12	P2.2	DAC output to robot controler	Should be able to reach 12b resolution with configurable Vref
13	P2.3	Push button called "up"	requires internal pull-up
14	P2.4	Push button called "down"	requires internal pull-up
15	P2.5	Digital signal from robot controller (pin4)	3.3V input
16	P2.6	Output to robot controller (pin3)	scaled down to 3.3V levels
17	P2.7	Bypass capacitor for ADCs and Vref
20	P3.0	RX from ZX2 sensor TX	ZX/RX crossed on board
21	P3.1	TX to ZX sensor RX	"
22	P3.2	5V monitor	resistive divider by 11 (R57/58), might be replaced by VDDA/2 input to ADC
23	P3.3	12V monitor	resistive divider by 11 (R52/55)
24	P3.4	Vin monitor	resistive divider by 11 (R51/54)
25	P3.5	output from diff amplifier (ZX output)	is 1.5*100*(4-20mA) V
26	P3.6	Pass from ZX2
27	P3.7	ADC Alert from ADS111x	for better ADS read timing
37	P4.0	Tune1/timing/bank0 to ZX
38	P4.1	Tune2/reset/bank1 to ZX
39	P5.0	Zero output to Zx
40	P5.1	LED1
41	P5.2	Key ok/LED2	switch in // with LED
42	P5.3	Dip switches for configuration	see table below

Dip switches thresholds:

dip2(MSB)	dip1(LSB)	threshold
0	0	>3V
0	1	>2V&&<2.5V
1	0	>2.5V&&<3V
1	1	<2V

Reading is done through the CSC_ADC that is ratiometric to +5V supply.

ADS111x configuration

Both ADS1114 and ADS1115 can be used in this project as only diff channel 0 is used. ADS1113 and ADS1118 might be compatible (to check)

The 4-20mA (which goes a bit beyond those limits) is fed to a high accuracy 100Ω resistor (R23), followed by antialising filter to prevent spectrum folding at digitization.

ADC itself is configured as such:

• MUX=000 (AINp=AIN0, AINn=AIN1)
• PGA=001 (4.096V range). 2.048V range can also be used, but then measurements will be caped to 10.72mm unless scaling is configured in ZX sensor
• COMP_QUE=11 (comparators disabled, at least for the moment)

ADS111x has address 0b1001000 on the I²C bus.

Design files

Test procedure

Assembly documents/BOM

FW design

Main concept

This FW is based on 3 layers:

1. HW interface with sensors, especially:
   
   • Digital readout of ZX2 (serial port)
   • Analog readout of ZX1/ZX2 through ADS111x ADC (I2C readout of ADC)
   • Analog readout of ZX1/ZX2 through µC ADC
   • Analog readout scaled for robot controler
   • Threshold applied to analog signal for robot controler
2. Processing layer:
   
   • will handle all threshold, internal conversions and processing of raw data from HW
   • Also, producing output to the robot controller is part if this layer
3. Communication layer to computer:
   
   • will handle all data transfers from/to computer, especially:
   • threshold settings
   • error and reliability management/debugging
   • system configuration the generate I/O to computer and robot controller

HW interactions

Detailed description

Protocol

Configurations

The MCP2221A has to be custom configured for proper system identification and also because of one input that is expected to be ADC input that is configured as digital output in factory configuration.

Main changes in configuration are:

• Self-powered
• Descriptor: MCP2221 ZXx readout
• Manufacturer: YGA/IIHE/2022
• GP3 = ADC3 input (very important, will prevent the analog output from differential amplifier to have correct voltage)
• ADC VRM=4.096V

Although configuration is done by HID commands that are cross-platform, Microchip provides an utility GUI to configure the MCP2221. Connection from analog readout to GP3 was added to the design as backup access to measurements from the MCP2221's ADC(10b). This measurement can de done independently from the µC running on the board. This is the reason for GP3 configuration as ADC.

MCP2221A configuration:

Known bugs and oddities

* Set ALLOWTOPICVIEW = AllAuthUsersGroup

-- YannickAllard - 2022-06-21